Well, here. Check it out. If you compare 1900 with 2012, you discover that pneumonia killed as many people in 1900 as heart disease did in 2012, for example. Or that diphtheria killed as many people in 1900 as "accidents" did in 2012, while in 1900 no one had ever heard of Alzheimer's disease - it didn't even have a name until 1906. It will not surprise you to learn that diphtheria and pneumonia mostly kill kids while Alzheimer's and heart disease mostly kill senior citizens. Take a look at that chart again. If you read it wrong, it looks like the rate of cancer death has tripled in the past hundred years. It's more accurate to say that the past 100 years have made people a lot more likely to survive the tuberculosis and diphtheria and influenza to die of heart disease and stroke. Statistically speaking, if it's 1900 I'm 6 years from the grave. 2015? I'm barely halfway there. (and happy as fuck, by the way, to skip out on that whole "Great War" thing. Man, what a dip) And that, dear Ben, is the purpose of medicine.
US didn't lose that many people in the war. Relative to our population, we lost slightly more than 0.1%, so even dying somewhat young as many of those men did, it would be hard to parse the signal from the noise. The flu? 0.7%, and you can bet that lots of the dead were babies, which weights the average down quite a bit. Interestingly, in looking up the numbers, I found some reports that say that about half the US soldiers who died in WWI actually died of the flu and weren't enemy casualties.